论文标题
通过温度依赖的第二次谐波产生成像探测过渡金属二分法中谷种群不平衡
Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
论文作者
论文摘要
动量空间中的简并最小值 - 山谷 - 提供了可用于信息传输和存储的额外自由度。值得注意的是，这种最小值自然存在于过渡金属二核苷（TMDS）的带结构中。当这些原子上的薄晶体与强烈的激光相互作用时，第二个谐波产生的（SHG）场就继承了特殊特征，这些特征不仅反映了真实空间中损坏的反转对称性，还反映了往等空间中的山谷各向异性。每当两个山谷之间存在山谷人口不平衡（VPI）时，后者就存在。在这项工作中，表明温度引起的SHG强度依赖性对激发场极化的变化是TMDS中VPI的独特指纹。特别是对这种变化的分析，可以计算山谷诱导的固有二阶敏感性比。与温度依赖性的光致发光（PL）测量值的谷化极化和连贯性不同，所提出的极化解析SHG（PSHG）方法对激发场波长不敏感，这是一个优势，它是监测在大型晶体或堆叠区域中监测VPI的理想选择，该优势是组成不同TMD的大型晶体或堆叠区域。
Degenerate minima in momentum space - valleys - provide an additional degree of freedom that can be used for information transport and storage. Notably, such minima naturally exist in the band structure of transition metal dichalcogenides (TMDs). When these atomically thin crystals interact with intense laser light, the second harmonic generated (SHG) field inherits special characteristics that reflect not only the broken inversion symmetry in real space, but also the valley anisotropy in reciprocal space. The latter is present whenever there exists a valley population imbalance (VPI) between the two valleys. In this work, it is shown that the temperature-induced changes of the SHG intensity dependence on the excitation fieldpolarization, is a unique fingerprint of VPI in TMDs. Analysis of such changes, in particular, enables the calculation of the valley-induced to intrinsic second order susceptibilities ratio. Unlike temperature-dependent photoluminescence (PL) measurements of valley polarization and coherence, the proposed polarization resolved SHG (PSHG) methodology is insensitive to the excitation field wavelength, an advantage that renders it ideal for monitoring VPI in large crystalline or stacked areas comprising different TMDs.
